Marine Ecosystems – Coral Reefs
I. Coral Reefs: all life in this habitat
depends on each other to maintain a
balance.
a. Phylum: Cnidaria – multicellular
animals characterized by two cell
layers, saclike digestive tract,
tentacles, radial symmetry & a
nerve net
b. Nematocycts – specialized cells
used to sting & capture prey
c. Polyp – a cnidarian attached to a
Substrate
II. Hard Corals:
a. Secrete a skeleton of calcium
carbonate (limestone), called a
calyx (a cup-shaped stony
structure that houses the coral
polyp), which remains after the
polyp has died
b. The calyxes support the reef
inhabitants.
Examples: antler, brain, elkhorn,
plate, saucer & staghorn
Brain Coral
Antler Coral
Plate Coral
III. Soft Corals:
a. Secrete a skeleton of keratin (a
protein similar to that of
fingernails)
b. Soft corals will decompose once
dead
Examples: sea fans, sea pens, sea
whips, organpipe coral, umbrella
coral, sea pansies & blue and red
corals
Sea Fan
Organ pipe Coral
Umbrella Coral
IV. 3 Types of Coral Reefs:
a. Fringing reef: grow in the
shallows of continents & islands
b. Barrier reef: serve as protective
breakwaters to coastal areas
i. example: Great Barrier Reef –
the longest in the world, 1250
miles long, located off the
coast of Australia
c. Atoll: a coral island; the reef
itself nearly or completely
encloses a lagoon
V. Commensalism: a symbiotic
relationship in which one species
benefits while the other species is
not affected by the relationship
a. Zooxanthellae: a single celled
green algae; lives within the
tissues of corals
i. assists hard corals in
manufacturing calcium
carbonate
ii. gives surrounding animals
food & oxygen through
photosynthesis
VI. Coral Habitat:
a. narrow temp. range: 70-84°F,
with the greatest variety
occurring between 77-84°F
b. shallow, calm waters where light
can penetrate
c. tropical waters at approximately
30° north/south of the equator
(lifeless sea, oasis to life)
i. low in dissolved oxygen
ii. low in nutrients
iii. low in plankton
VII. Some coral inhabitants:
a. Shrimp, crabs, butterfly fish, lion
fish, parrot fish, moray eels,
trigger fish
Butterfly Fish
Lion Fish
Moray Eel
VIII. Some soft coral predators:
a. Nudibranchs – shell-less
members of the phylum Mollusca,
feed on soft corals; cowries,
flamingo-tongue snails, sundial
snails
Nudibranchs
Cowries
Flamingo-tongue snail
IX. Some hard coral predators:
a. Crown-of-thorns sea star – up to
2 feet of corals destroyed per day;
Crown-of-thorns